Protection against dc faults is one of the main technical hurdles faced when operating converter-based HVdc systems. Protection becomes even more challenging for multi-terminal dc (MTdc) systems with more than two terminals/converter stations. In this paper, a hybrid primary fault detection algorithm for MTdc systems is proposed to detect a broad range of failures. Sensor measurements, i.e., line currents and dc reactor voltages measured at local terminals, are first processed by a top-level context clustering algorithm. For each cluster, the best fault detector is selected among a detector pool according to a rule resulting from a learning algorithm. The detector pool consists of several existing detection algorithms, each performing differently across fault scenarios. The proposed hybrid primary detection algorithm: i) detects all major fault types including pole-to-pole (P2P), pole-to-ground (P2G), and external dc fault; ii) provides a wide detection region covering faults with various fault locations and impedances; iii) is more robust to noisy sensor measurements compared to the existing methods. Performance and effectiveness of the proposed algorithm are evaluated and verified based on time-domain simulations in the PSCAD/EMTDC software environment. The results confirm satisfactory operation, accuracy, and detection speed of the proposed algorithm under various fault scenarios.

中文翻译：

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多端高压直流系统的混合直流故障初级保护算法

防止直流故障是运行基于转换器的 HVdc 系统时面临的主要技术障碍之一。对于具有两个以上终端/换流站的多终端直流 (MTdc) 系统，保护变得更具挑战性。在本文中，提出了一种用于 MTdc 系统的混合初级故障检测算法来检测范围广泛的故障。传感器测量值，即在本地终端测量的线路电流和直流电抗器电压，首先由顶级上下文聚类算法处理。对于每个集群，根据学习算法产生的规则在检测器池中选择最佳故障检测器。检测器池由几种现有的检测算法组成，每种算法在不同的故障场景中表现不同。提出的混合初级检测算法：i) 检测所有主要故障类型，包括极对极 (P2P)、极对地 (P2G) 和外部直流故障；ii) 提供广泛的检测区域，覆盖具有各种故障位置和阻抗的故障；iii) 与现有方法相比，对嘈杂的传感器测量更稳健。基于 PSCAD/EMTDC 软件环境中的时域仿真，对所提出算法的性能和有效性进行了评估和验证。结果证实了该算法在各种故障场景下的令人满意的运行、准确性和检测速度。基于 PSCAD/EMTDC 软件环境中的时域仿真，对所提出算法的性能和有效性进行了评估和验证。结果证实了该算法在各种故障场景下的令人满意的运行、准确性和检测速度。基于 PSCAD/EMTDC 软件环境中的时域仿真，对所提出算法的性能和有效性进行了评估和验证。结果证实了该算法在各种故障场景下的令人满意的运行、准确性和检测速度。